Rangel allegedly used a rent-stabilized apartment in this Harlem building as an office, despite a pledge it was to be used "for living purposes only," -- a fraud ethics counsel called "open and notorious." Photo: Angel Chevrestt

Forget about a smoking gun — this was more like a smoldering arsenal.

Investigators probing Rep. Charles Rangel yesterday unleashed an avalanche of never-before-seen evidence against the lawmaker, ranging from classified corporate memos to a 50-year-old certificate of occupancy to his Harlem home.

The treasure-trove of documents — an astounding 4,200 pages of evidence that encompasses the 549 exhibits that will be used in the case — were posted on the Web site of the House Committee on Standards of Official Conduct just as the trial was getting under way.

The exhibits — amassed during a two-year probe — provide a virtual roadmap in the case against Rangel, who is facing 13 ethics charges.

It includes sworn affidavits from a host of Big Apple boldfaced names, including former AIG honcho Maurice Greenberg and Verizon CEO Ivan Seidenberg.

The evidence also includes dozens of communications from Rangel and his staff regarding a center to be named after the 20-term congressman at City College — including letters on US House stationery seeking financial backing for the proposed center that were sent to a litany of big shots.

Letters seeking money and bearing images of the American bald eagle and the coat of arms of the Great Seal of the United States were sent to Donald Trump, Greenberg and David Rockefeller.

Investigators also introduced in their evidence — which they presented yesterday to an eight-person, bipartisan panel — detailed records regarding Rangels’ Harlem apartment building, where he has lived for decades.

They included the building’s 1961 certificate of occupancy — apparently to show it was a residential building — as well as the original lease Rangel signed in 1996 for Apartment 10U.

Rangel was already living in the building in another apartment and took 10U to use for his campaign.

“You shall use the apartment for living purposes,” the lease states.

The documents also include e-mails from Walter Swett, Rangel’s campaign director, asking landlords about repairs.

A January 1993 letter included in the evidence pile shows that Rangel was aware he had to report income from his Dominican vacation home.

“The House Ethics Committee requires the disclosure . . . of any assets and unearned income,” Rangel wrote to the villa. “It certainly would be politically embarrassing if I were unable to provide an accurate accounting of my holdings.”

The e-mails, letters and memos from private meetings show Rangel’s cozy relationship with the big-bucks donors he was hitting up for money.

A New York Life internal memo to CEO Sy Sternberg — whom Rangel asked for donations — reveals instructions from his staff on how to sweet-talk the pol at a campaign event.

“It would be nice to refer to him as ‘Mr. Chairman,’ signaling the possibility that he would become chairman of the House Ways and Means Committee,” read the 2006 memo.

Rangel did become chairman shortly after the meeting, but, because of the ethics scandal, quit earlier this year.

“Thank him for his help on fighting the estate-tax repeal,” the memo read.

Eugene Isenberg — CEO of an oil-drilling company that donated $1 million to Rangels’ City College center — sent an e-mail to the congressman after they were introduced by then-Manhattan District Attorney Robert Morgenthau.

“It really was a pleasure meeting with you in Bob’s office on Monday, Sept. 18,” Isenberg wrote.

Around the time Isenberg made the donation, Rangel — who had always maintained none of his fund-raising targets were getting any benefits from his role in Congress — helped preserve a tax loophole that benefited Isenberg’s company.